Constant depth fracture groove

ABSTRACT

In an embodiment, a method of manufacturing customized ceramic labial/lingual orthodontic brackets by additive manufacturing may comprise measuring dentition data of a profile of teeth of a patient, based on the dentition data, creating a three dimensional computer-assisted design (3D CAD) model of the patient&#39;s teeth, and saving the 3D CAD model, designing a virtual 3D CAD bracket structure model for a single labial or lingual bracket structure based upon said 3D CAD model, importing data related to the 3D CAD bracket structure model into an additive manufacturing machine, and directly producing the bracket with the additive manufacturing machine by layer manufacturing from an inorganic material including at least one of a ceramic, a polymer-derived ceramic, and a polymer-derived metal.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a continuation of and claims priority under 35U.S.C. § 120 to U.S. patent application Ser. No. 15/962,261, filed onApr. 25, 2018, entitled “MANUFACTURE OF PATIENT-SPECIFIC ORTHODONTICBRACKETS WITH IMPROVED BASE AND RETENTIVE FEATURES,” which isincorporated herein by reference in its entirety.

BACKGROUND OF THE INVENTION 1. Field of the Invention

An embodiment of present invention relates generally to themanufacturing of ceramic labial/lingual orthodontic brackets forstraightening the teeth and correcting malocclusion. More specifically,an embodiment of the invention relates to the methodology of directmanufacture of customized labial/lingual orthodontic brackets by using aceramic slurry-based additive manufacturing (AM) technology.

2. Description of the Related Art

Orthodontics has been widely adapted in clinics to correct malocclusionand straighten teeth. The traditional method is to adhere preformedbrackets onto the teeth and run elastic metal wires of round, square, orrectangular cross-sectional shape through the bracket slots to providethe driving force. The adaptation of the bracket to the individual toothis performed by filling the gap between the tooth surface and bracketsurface with adhesive. This thereby bonds the bracket to the tooth suchthat the bracket slot, when the teeth are moved to their final position,lies in a near flat (depending on manufacturing accuracy) horizontalplane.

Preformed edgewise brackets may have no prescription, requiringadjustment of the archwire. Alternatively, the edgewise brackets mayhave an idealized prescription of angulation, inclination, or in/outvariation for specific teeth in what is referred to as a “straight-wireappliance”. Because the bracket pad is typically not custom made for anindividual patient's tooth, the clinician is responsible for the bracketplacement, which may introduce a source of error, which commonlyincreases patient visits and overall treatment time. These brackets aretypically off-the-shelf products, and currently there are no customdesigned ceramic brackets available commercially. A misplacement inbonding a bracket to a tooth can be corrected by compensation bends inthe wire or by debonding and repositioning of the bracket, both of whichincrease time and cost. Custom metal lingual brackets are currentlyavailable that are fabricated at a central location from 3D scans orimpressions of the dentition and mailed back to the clinician andtransferred to the patient via indirect bonding. Selective laser melting(SLM) is a 3DAM technique that has been used to create custom metallingual brackets (for example, see U.S. Pat. No. 8,694,142 B2), but thistechnique suffers from insufficient resolution and surface finish. Whiletrue custom labial brackets have been used, custom positioning of astandard, non-custom bracket can be created via indirect bonding whichitself has inherent error within the bracket itself. Many current truecustom labial systems (SURESMILE™ Inc.) rely heavily on putting custombends in the wire based on a 3D scan rather than creating a truestraight-wire appliance. For example, U.S. Pat. No. 8,690,568 providesfor a method to weld a metal bracket slot to a stock metal bracket baseinto a custom position, but does not describe a method for creating acustom bracket base or to create an aesthetic, non-metal bracket. Thesepartially custom metal brackets suffer from inaccuracy in slot positionand premature debonding due a stock bracket base that doesn't match thetooth morphology, and are unappealing to older patients who prefer tohave non-metal brackets for aesthetic concerns.

Ceramic brackets have been commercially available and studied since the1980s and are a desirable material compared to metal brackets due totheir excellent esthetics, resistance to creep, rigidity,biocompatibility, corrosion resistance, stability in the oralenvironment and non-toxic nature. Ceramic brackets are predominantlymanufactured by injection molding, which has manufacturing limitations.For example, it may be difficult or impossible to use injection moldingto create undercuts that may enhance a bracket's mechanical bondstrength to a tooth adhesive. Currently, no system for creating estheticcustom lingual or labial ceramic orthodontic brackets exists.

A need arises for more efficient and accurate methods for manufacturingpatient-specific lingual and labial ceramic orthodontic brackets, andmore aesthetic/accurate patient-specific labial brackets.

SUMMARY OF THE INVENTION

An embodiment of the present invention provides improved techniques forcreating custom lingual or labial ceramic orthodontic brackets, andwhich provides the capability for in office fabrication of suchbrackets.

An embodiment of the present invention may be used to solve problemsoccurring in the current manufacturing techniques of straight wireappliance orthodontic brackets. For example, in one embodiment, it mayprovide a direct manufacturing method of customized lingual/labialbrackets by utilizing any number of ceramic slurry-based AMtechnologies, examples of which may include digital light processing(DLP), laser photopolymerization stereolithography, jet printing(including particle jetting, nanoparticle jetting), layer slurrydepositioning (LSD), or laser-induced slip casting. A slurry is definedas inorganic particles dispersed in a liquid, and may bephotopolymerizable or may polymerize by other mechanisms. Likewise,similar methods may be used to create metal brackets wherein theinorganic materials in the slurry are metal. Examples of items that maybe produced include customized labial/lingual brackets according toindividual dental and craniofacial features, which may have directtooth-matching retentive features designed into the bracket base.Ceramic slurry-based AM may be performed in a device small enough tocomfortably fit in a private orthodontic lab and can currently beobtained at a reasonable price, given the market price and in-officevolume for non-custom and custom brackets.

For example, in one embodiment, a method of manufacturing customizedceramic labial/lingual orthodontic brackets by ceramic slurry-based AMmay comprise measuring dentition data of a profile of teeth of apatient, based on the dentition data, creating a three dimensionalcomputer-assisted design (3D CAD) model of the patient's teeth usingreverse engineering, and saving the 3D CAD model on a computer,designing a 3D CAD bracket structure model for a single labial orlingual bracket structure, importing data related to the 3D CAD bracketstructure model into a ceramic slurry-based AM machine, directlyproducing the bracket (green part) in the ceramic slurry-based AMmachine by layer manufacturing, and processing the brackets in asintering and debinding oven prior to direct use or otherpost-processing steps related to surface properties.

The 3D CAD bracket structure model may include data representing atleast a) the bracket pad (base) that has recesses and/or undercuts intothe bonding surface of the bracket, to contact a particular tooth'ssurfaces, b) slots for positioning according to the orthodontia needs ofthe patient, c) a bracket material, d) the particular tooth's profile,and e) a bracket guide to guide 3-dimensional placement of the bracketonto the tooth.

The ceramic slurry-based AM machine may comprise a molding compartmentcomprising a platform and a plunger to directly produce the bracket bylayer manufacturing, a material compartment, and an LED light source fordigital light processing, or a print-head with at least one dispensingnozzle as used in “jet” printing, wherein the bracket is produced bylayer manufacturing using slicing software to separate the 3D CADbracket structure model into layers and to get a horizontal sectionmodel for each layer so that a shape of each layer produced by theceramic slurry-based AM machine is consistent with the 3D CAD structuredata. The ceramic slurry-based AM machine may comprise a vat adapted tohold the bracket during manufacturing, a horizontal build platformadapted to be held at a settable height above the vat bottom, anexposure unit, adapted to be controlled for position selective exposureof a surface on the horizontal build platform with an intensity patternwith predetermined geometry, a control unit, adapted to receive the 3DCAD bracket structure model and, using the 3D CAD bracket structuremodel to polymerize in successive exposure steps layers lying one abovethe other on the build platform, respectively with predeterminedgeometry, by controlling the exposure unit, and to adjust, after eachexposure step for a layer, a relative position of the build platform tothe vat bottom, to build up the object successively in the desired form,which results from the sequence of the layer geometries. The exposureunit may further comprise a laser as a light source, a light beam ofwhich successively scans the exposure area by way of a movable mirrorcontrolled by the control unit.

Directly producing the bracket by layer manufacturing may furthercomprise an apparatus comprising a vat with an at least partiallytransparently or translucently formed horizontal bottom, into whichlight polymerizable material can be filled, a horizontal build platformadapted to be held at a settable height above the vat bottom, anexposure unit adapted to be controlled for position and selectiveexposure of a surface on the build platform with an intensity patternwith predetermined geometry, comprising a light source refined bymicromirrors to more precisely control curing, a control unit adaptedfor polymerizing in successive exposure steps layers lying one above theother on the build platform, controlling the exposure unit so as toselectively expose a photo-reactive slurry in the vat, adjusting, aftereach exposure for a layer, a relative position of the build platform tothe vat bottom, and building up the bracket successively in the desiredform, resulting from the sequence of the layer geometries. The exposureunit may further comprise a laser as a light source, a light beam ofwhich successively scans the exposure area by way of a movable mirrorcontrolled by the control unit.

A scanning accuracy may be less than about 0.02 mm. A manufacturingaccuracy may be from about 5 to about 60 μm, and wherein the accuracymay be achieved by using a between layer additive error compensationmethod that predicts an amount of polymerization shrinkage. Manufacturedlayers of the bracket comprise a material selected from the groupconsisting of high strength oxides, nitrides and carbides ceramicsincluding but not limited to: Aluminum Oxide (Al₂O₃), Zirconium Oxide(ZrO₂), Alumina toughened Zirconia (ATZ), Zirconia-toughened alumina(ZTA), Lithium disilicate, Leucite silicate, Nitrides (e.g. SiN4), andmono- or polycrystalline ceramic. The smallest length from a bracket padto slot depth may be from about 0.2 mm to about 3 mm depending on thebracket offset required and desire to reduce the bracket profile forpatient comfort.

The 3D CAD model may be saved as an .stl file or other 3D vector file.The thickness of the manufactured layers may be from about 5 to about100 micrometers (μm), and the machine may use a X-Y pixel resolutionfrom about 5 to about 100 μm. Different curing strategies (CSs) anddepths of cure (Cd) may be used. A selection of material for producinglayers of the bracket may be based on different force demands. Theprinted bracket guides may have a single bracket attachment for a singlebracket. An adhesive material may be used to hold the bracket on theceramic archwire. The adhesive material may be sticky wax. Indirectbonding/custom bracket placement may occur via a tray (for example, asilicone based or vacuum formed tray) that carries the said customceramic brackets to the ideal tooth location.

The printed brackets may have a metal insert that contacts the archwirein the slot. The printed brackets may be of a traditional twin design orare modified to be self-ligating or active ligating and are designed toaccommodate 0.018 in or 0.022 in archwires in the slot, but slot heightmay vary from about 0.018 to about 0.022. The bracket angulation,offsets, torque, and prescription may be determined based on a chosentreatment. The structural properties of the base may be altered tofacilitate easier debonding of the bracket following treatment. A partof the bracket may be a preformed green ceramic body that functions todecrease the time and complexity of the printed bracket. The method mayfurther comprise producing a bracket guide comprising a rigid ceramicrectangular archwire or other archform that dictates a position of eachbracket on a tooth in every plane with at least two occlusal/incisalsupports adapted to help place brackets via an indirect bonding system.A part of the bracket that holds or connects the bracket to the toothsurface may be designed based on a surface profile of the tooth. Thebracket may have a color that is matched to a color of a tooth to whichthe bracket is to be attached. The bracket may be clear. The bracket mayhave a selected color unrelated to a color of a tooth to which thebracket is to be attached.

The ceramic slurry-based AM machine may include a light source that is alaser or LED light source. A light source of the DLP machine may radiatea wavelength between 400 and 500 nm. The DLP machine may include adigital light processing chip as light modulator. The digital lightprocessing chip may be a micromirror array or an LCD array.Alternatively, the ceramic slurry-based AM machine may use a jettechnology whereby a liquid ceramic slurry is jetted onto a build-platein layers, with or without another jet dispensing non-ceramic supportmaterial.

Measuring dentition data may be performed using a CT scanner, intra-oralscanner, a coordinate measuring machine, a laser scanner, or astructured light digitizer. Measuring dentition data may be performed byconducting 3D scanning on a casted or 3D printed teeth model.

The light-polymerizable material may be selected from the groupconsisting of high strength oxides, nitrides and carbides ceramicsincluding but not limited to: Aluminum Oxide (Al₂O₃), Zirconium Oxide(ZrO₂), Alumina toughened Zirconia (ATZ), Zirconia-toughened alumina(ZTA), Lithium disilicate, Leucite silicate, Nitrides (e.g. SiN4), andmetals. A slot position relative to the tooth may be customized bymanufacturing a custom base or by manufacturing a custom slot positionwhere a base is unchanged.

In an embodiment, a method of manufacturing customized ceramiclabial/lingual orthodontic brackets by additive manufacturing maycomprise measuring dentition data of a profile of teeth of a patient,based on the dentition data, creating a three-dimensionalcomputer-assisted design (3D CAD) model of the patient's teeth, andsaving the 3D CAD model, designing a virtual 3D CAD bracket structuremodel for a single labial or lingual bracket structure based upon said3D CAD model, importing data related to the 3D CAD bracket structuremodel into an additive manufacturing machine, and directly producing thebracket with the additive manufacturing machine by layer manufacturingfrom an inorganic material including at least one of a ceramic, apolymer-derived ceramic, and a polymer-derived metal.

In embodiments, the additive manufacturing machine may use a slurrybased process. The slurry-based process may include at least one oflithography-based manufacturing, inkjet printing, slip casting, laserlithography additive manufacturing, direct light processing, andselective laser melting. The 3D CAD bracket structure model may includedata defining at least one slot adapted to receive an archwire,including data defining a compensation angle for walls of the slot tocompensate for shrinkage due to over-polymerization and achieve parallelslot walls.

In embodiments, the 3D CAD bracket structure model may include datadefining a fracture wall around a perimeter of a base of the bracket.The fracture wall may have a thickness of about 10 to about 150 μm,inclusive. The fracture wall may be adapted so as to fracture uponapplication of a normal force. The normal force may be applied in atleast one of a mesial-distal direction, an occlusal-gingival direction,or to any opposite corners. The fracture wall may be adapted to providepredictable fracture of the wall upon application of the normal force,enabling debonding of the bracket though a combination of tensile andpeeling forces. The combination of tensile and peeling forces may beless than a shear bond strength of a bonded bracket. The normal forcemay be about 10 to about 180 Newtons, inclusive.

In embodiments, the 3D CAD bracket structure model may include datadefining a contour of a surface of a base of the bracket. The contourmay be adapted to a shape of a tooth to which the bracket is to bebonded. The contour may be further adapted based on at least one of anin/out and offset of the bracket, a tip of the slot, and a torque.

In embodiments, the 3D CAD bracket structure model may include datadefining a fracture groove in a base of the bracket. The fracture groovemay be in a middle vertical third of the bracket. The fracture groovemay include a weakened area including a tooth curved depression in thebracket base in an occlusal-gingival direction. The fracture groove maymatch a contour of the tooth for that portion of the bracketpositioning. The fracture groove may be constant in depth from the toothsurface. The fracture groove may have a depth of about 0.10 mm to about1.2 mm, inclusive. The fracture groove may vary in depth from the toothsurface. The fracture groove may have a variance in depth of about 1 toabout 50%, inclusive, of a distance from the tooth surface to a deepestpart of fracture groove. The fracture groove may be in the middlevertical third of the bracket. The fracture groove may have a negativedraft angle.

In embodiments, the 3D CAD bracket structure model may include datadefining a plurality of retentive structures in a base of the bracket.Each retentive structure may be a three-dimensional figure with apositive draft angle greater than 0°. Each retentive structure may be athree-dimensional figure selected from a group of three-dimensionalfigures including semi-lunar cones, full-circle cones, squares,rectangles, retentive lattices, and or meshes. Each retentive structuremay have a cross-section that is generally trapezoidal, and having aneutral plane oriented toward a tooth structure or surface that is widerthan a base plane oriented toward a bracket body. Each neutral plane maybe flat. Each neutral plan may be parallel to the base plane. At leastsome neutral planes may not be parallel to the base plane. At least someneutral planes may not be parallel to the base plane such that anoverall pattern of the retentive structures is generally contoured to ashape of a tooth surface to which it is to be bonded. At least someneutral planes may be contoured to a shape of a tooth surface to whichit is to be bonded.

In embodiments, the 3D CAD bracket structure model may include datadefining at least some corners of the bracket as being rounded. Gingivalcorners of the bracket may be rounded. The rounded corners of thebracket may have a radius of curvature of about 0.05 to about 2.0 mm.The bracket may be adapted to be bonded to the lingual or labialsurfaces of a tooth.

In embodiments, the bracket may be made of an inorganic material with atleast one component selected from a group of materials including anoxide ceramic, a nitride ceramic, a carbide ceramic, Aluminum Oxide(Al2O3), Zirconium Oxide (ZrO2), Alumina-toughened Zirconia (ATZ),Zirconia-toughened alumina (ZTA), Lithium disilicate, Leucite silicateand Silicon Nitride. The 3D CAD bracket structure model may include datadefining a mesial-distal or horizontal slot adapted to receive anarchwire, a vertical slot adapted to receive at least a portion of thearchwire within a middle third of the bracket, or both. The verticalslot may be further adapted to accept a digitally designed lingualmultiloop wire.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an exemplary flow diagram of an embodiment of a process fordirect manufacturing lingual or labial orthodontic brackets.

FIG. 2 illustrates an example of a single bracket bracket-guide showinga lower molar and upper incisor tooth.

FIG. 3 illustrates an example of a bracket guide that may be a rigidceramic rectangular archwire that engages each bracket in every planewith two or more occlusal supports.

FIG. 4 illustrates an example of designed brackets having a custombracket pad that is matched to the lingual or labial surface of thetooth.

FIG. 5 illustrates a side view of an example of a designed bracket.

FIG. 6 illustrates a top view of an example of a designed bracket.

FIG. 7 is an exemplary block diagram of an embodiment of a computersystem in which the processes of the present invention may beimplemented.

FIG. 8 is an exemplary illustration of an embodiment of an orthodonticbracket.

FIG. 9 is an exemplary illustration of an embodiment of an orthodonticbracket.

FIG. 10 is an exemplary illustration of an embodiment of an orthodonticbracket.

FIG. 11 is an exemplary illustration of an embodiment of an orthodonticbracket.

FIG. 12 is an exemplary illustration of an embodiment of an orthodonticbracket.

FIG. 13 is an exemplary illustration of an embodiment of an orthodonticbracket.

FIG. 14 is an exemplary illustration of an embodiment of an orthodonticbracket.

FIG. 15 is an exemplary illustration of an embodiment of an orthodonticbracket.

FIG. 16 is an exemplary illustration of an embodiment of an orthodonticbracket.

FIG. 17 is an exemplary illustration of an embodiment of a retentivestructure.

FIG. 18 is an exemplary illustration of an embodiment of an orthodonticbracket.

FIG. 19 is an exemplary illustration of an embodiment of an orthodonticbracket.

FIG. 20 is an exemplary illustration of an embodiment of an orthodonticbracket.

FIG. 21 is an exemplary flow diagram of an embodiment of a process ofbracket design.

DETAILED DESCRIPTION OF THE INVENTION

An embodiment of the present invention provides improved techniques forcreating custom lingual or labial ceramic orthodontic brackets, providesimproved brackets, and which may further provide the capability forin-office fabrication of such brackets.

An exemplary flowchart of an embodiment a direct manufacturing process100 of lingual or labial orthodontic brackets by ceramic slurry-based AMis shown in FIG. 1. The process begins with 102, in which dentition datais measured and the parameters of the tooth profile are analyzed. Forexample, such measurement may use CT layer scanning a non-contact 3Dscanner or an intra-oral scanner directly on the patient's teeth, or mayuse 3D readings on a teeth model previously cast or 3D printed using acoordinate measuring machine, a laser scanner, or structured lightdigitizers. The scanning accuracy of such techniques is typically lessthan about 0.02 mm.

In 104, based on the given dentition data, a 3D CAD model of themeasured teeth is constructed based on the dentition data and saved inthe computer in a typical file format, such as the .stl, Additivemanufacturing File (AMF) format or any other 3D vector file. Theexterior structure of teeth is complicated, usually including irregularcurves. The software may then be used to re-arrange the teeth in themodel to the desired treatment outcomes that may be based on thelong-axis of a tooth.

In 106, additional information, such as the desired torque, offset,angulation of select brackets and occlusal/incisal coverage forplacement guide is entered.

In 108, the bracket (or brackets) is designed by the software based onthe input 3D CAD model of the measured teeth, the model of the desiredtreatment outcomes, and the input additional information. The output ofthe design process may be a 3D CAD model. Such a 3D CAD model may bedesigned for a single lingual/labial bracket structure, including thebracket guide and bracket pad in contact with teeth surface, as well asthe slots for the ideal position according to the orthodontiarequirement, ceramic bracket material, and tooth profile. A bracketguide may be a single bracket pad for a single bracket or may be a rigidceramic rectangular archwire with two or more occlusal supports, whichare designed to help place brackets via indirect bonding. If the guideis for a single bracket, the bracket guide may be printed such that itis serrated at its interface with the bracket such that it may besnapped or drilled off upon bonding.

3D CAD bracket structure models of labial or lingual brackets may bedesigned by computer according to the orthodontic requirements,material, and teeth morphology. Referring to FIG. 2, which illustratesan example of a single bracket bracket-guide showing a lower molar andupper incisor tooth with a connected, but detachable bracket guide thatmay have a weak point or serration at the guide-bracket interface. Thebracket model design may include the bracket pad 202 (bonding pad)contacting with the tooth surface, as well as the custom bracket slotlocated on its ideal position and a bracket guide 204. A bracket guide204 may be a single bracket pad 202 attached to a single bracket guide204, as shown in FIG. 2. Alternatively, as shown in FIG. 3, a bracketguide may be a rigid ceramic rectangular archwire that engages eachbracket in every plane with two or more occlusal supports 304 that aredesigned to help place brackets via indirect bonding. The horizontalwire and the occlusal/incisal pads control for vertical position.Vertical notches such as 306 on the wire control the horizontal positionof the bracket on the ceramic wire.

3D CAD bracket structure models are processed to generate manufacturingcontrol data for use by the production equipment. For example, where theceramic slurry-based AM equipment is used to produce the brackets, thesoftware slices the 3D CAD bracket structure models to separate it intothin layers and get the horizontal section model for each layer. Basedon this section model, the DLP equipment can directly produce ceramicbrackets, ensuring the shape of each layer is consistent to the 3D CADstructure data. For example, the thickness of such layers may be about20 μm to about 50 μm (micrometers or microns) with a manufacturingaccuracy of about 5 μm to about 10 μm by using between-layer additiveerror compensation.

Returning to 108 of FIG. 1, the 3D CAD bracket structure model istransmitted to or imported into a 3D production machine, such as aceramic slurry-based AM machine and the ceramic brackets are produced

DLP is another ceramic additive manufacturing (AM) process that works bystacking layers of a photocurable resin with a ceramic oxide such asAluminum Oxide (Al₂O₃) or Zirconium Oxide (ZrO₂), Nitrides or Silicatessolid loading, and followed by a thermal debinding and sintering step.The higher resolution of this process is made possible by the LEDlight's digital mirror device (DMD) chip and optics used.(Stereo-)Lithography-based ceramic manufacturing (LCM) has improved thisprocess making it more accurate with higher resolution (40 μm) andrigidity. The LCM process involves the selective curing of aphotosensitive resin containing homogenously dispersed oxide or glassceramic particles that can be fabricated at very high resolution due toimaging systems which enable the transfer of layer information by meansof ever-improving LED technology, though a laser may also be used forphotopolymerization.

In 110, post-processing may then be applied. For example, a thermaltreatment (for binder burnout) and a sintering process may be applied toachieve optimal or improved ceramic density. For example, the debindingand sintering phase may include removing the green bracket from thedevice, exposing the blank to a furnace to decompose the polymerizedbinder (debinding), and sintering of the ceramic material.

The pad (bonding pad) of the bracket may be less than about 0.4 mm thickfrom the tooth. The bracket placement guide may be placedocclusally/incisally to guide the correct placement of the bracket onthe tooth. Examples of raw materials of the brackets may include powderof high strength oxide ceramics such as Aluminum Oxide (Al₂O₃) andZirconium Oxide (ZrO₂), or other high strength ceramic compositions.

The base of bracket may be adhered to the tooth surface and the bracketslot may be matched to the archwire. According to requirements ofmechanical properties, different composition of material may be requiredfor the layers during the DLP manufacturing process. After being builtup, the brackets may have a gradient and better performance.

Further, the bracket surface may be processed based on clinical demand.

Returning to FIG. 1, in 112, the bracket is ready to be placed.

Typically, the thickness of the bracket pad may less than 1 mm forlingual brackets and less than 1.5 for labial brackets. Suitablemanufacturing materials may include high strength oxides, nitrides andcarbides ceramics including but not limited to: Aluminum Oxide (Al₂O₃),Zirconium Oxide (ZrO₂), Alumina-toughened Zirconia (ATZ),Zirconia-toughened alumina (ZTA), Lithium disilicate, Leucite silicateor Silicon Nitride. The bracket pad may be adhered to the tooth surfacewith well-known dental adhesives. The bracket slot may be matched to thearchwire, which may be straight or custom bent. Depending upon themanufacturing process used, different ceramics or composition of powdermay be required for the layers. For example, if a selective lasermelting manufacturing process is used, an LED light source may be usedfor the selective curing of a photosensitive resin containing the oxideor glass ceramic particles. Different layers may use different ceramicsor compositions of powder.

The bracket pad, which holds or connects the bracket to the toothsurface, may be designed specifically according to the tooth surfaceprofile, instead of a generalized gridding pattern. The customizedbrackets can meet individual case demand, such as increased anteriorlabial crown torque required in certain types of cases. For example, asshown in FIG. 4, the curve on tooth surface and the designed bracket,the tooth side of the bracket (bracket pad) is matched to the lingual orlabial surface of the tooth, for example for lingual bracket 402 andlabial bracket 404.

A side view of an exemplary printed bracket 500 is shown in FIG. 5. Theslot 502 on the bracket may have high accuracy in size, shape, andangler, and may have low thickness and is designed to accommodate arectangular wire when completely filled. Slot 502 may be manufactured toany desired size and shape, but typically, slot 502 is manufactured witha greater depth than height or width. The base 504 of the bracket mayhave different height because of the selected material or desiredorthodontic result. Likewise, the pad 506 of the bracket may highlymatch the tooth surface and maximize the tooth contact surface. This mayallow for more accurate bracket placement by the clinician and betterbond approximation to the tooth. Also, because each slot has its ownposition and shape to cooperate with the archwire, twisting error may beminimized and improved orthodontic result may be actualized. In a numberof embodiments, these features may be manufactured as one piece and thatthe customization of the slot relative to the tooth may be a function ofthe slot changing position or the bracket base moving. In manyembodiments, no machining of the features is required to produce asuitable bracket.

A top view of an exemplary printed bracket 600 is shown in FIG. 6.Bracket guides may be printed that extend an arm occlusally/incisallythat attaches to a pad that covers enough of the structure of the tooth602 (mesial/distal of occlusal/incisal surface or marginal ridge) suchthat brackets are placed in the computer-generated ideal location tocreate the desired tooth position. A bracket guide may be any number ofindirect bonding (IDB) guides, jigs or trays that may be from aplurality of materials that are made by traditional methods or by aCAD/CAM methods which include SLA, DLP or Jet printing. Alternatively,the bracket-positioning device may be a rigid ceramic rectangulararchwire that engages each bracket in every plane with two or moreocclusal supports that are designed to help place brackets via indirectbonding. The horizontal ceramic wire and the occlusal/incisal padscontrol for vertical position, vertical notches on the wire control thehorizontal position of the bracket on the ceramic wire guide.

Bracket 600 may further include an attachment such as a hook 604 thatprovides the capability to use additional delivery systems such aselastomers, springs or other attachments that create vectors of force.In a number of embodiments, these features may be manufactured as onepiece, protruding from any predesigned area to create the proper forcevectors desired, and no machining of the features is required to producea suitable bracket.

Using the ceramic slurry-based AM technique can turn the designed modelinto a ceramic product rapidly. The bracket manufacturing involves fewsteps and can be done on site, saving time and cost.

The described techniques may be used to manufacture brackets fromconsisting of high strength oxides, nitrides and carbides ceramicsincluding but not limited to: Aluminum Oxide (Al₂O₃), Zirconium Oxide(ZrO₂), Alumina-toughened Zirconia (ATZ), Zirconia-toughened alumina(ZTA), Lithium disilicate, Leucite silicate or Silicon Nitride.

The described techniques may be used to attain a true straight wireappliance where bracket placement accuracy is improved, thus reducingtreatment time and error; or may also be used in conjunction with acustom-bent arch wire to achieve ideal results.

Patients currently pay higher fees for white-colored ceramic bracketsover metal due to their increased esthetics. For example, many patientsdesire a bracket that matches the color of the tooth to which thebracket is attached. This may cause the bracket to be less visible andprovide improved appearance. As another example, embodiments of thepresent invention may provide the capability to produce clear brackets,which may provide still improved appearance. Additionally, embodimentsof the present invention may provide the capability to produce bracketsin almost any color desired or selected, for example, in bright colorsfor use in children and some adults. Likewise, embodiments of thepresent invention may provide the capability to produce brackets havingvisible shapes that are not dictated by function, such as in the shapeof animals, vehicles, toys, etc., for example, for use in children andsome adults.

The described techniques may be made cost-effective to the point wherean individual orthodontic practice could purchase the required equipmentand software. This would provide the capability to simplify theirbracket inventory instead of stocking brackets of differentprescriptions.

Digital light processing (lithography-based) of ceramics has manyadvantages for orthodontic bracket fabrication, in comparison toselective laser sintering/melting (SLM) which uses thermal energy, and3-D printing (3DP) systems that use a binder and polymer-derivedceramics (PDCs). For example, DLP may provide higher surface quality,better object resolution, and improved mechanical properties. PDCsstructured using light in a stereolithographic or mask exposure processmay also be used as a ceramic AM method for bracket fabrication.

Custom lingual brackets may be fabricated by this method, which mayreceive a pre-bent customized archwire as described by US 2007/0015104A1. Custom labial brackets may also receive pre-bent wires.

The procedure for the layering additive manufacturing (AM) methodologyof the labial/lingual orthodontic brackets by lithography-based DLP (forexample, U.S. Pat. No. 8,623,264 B2) is as follows.

An example of a lithography-based DLP process is described in U.S. Pat.No. 8,623,264 B2, which is incorporated herein by reference, but may bebriefly summarized as follows: a light-polymerizable material, thematerial being located in at least one trough, having a particularlylight-transmissive, horizontal bottom, is polymerized by illumination onat least one horizontal platform, the platform having a pre-specifiedgeometry and projecting into a trough, in an illumination field, whereinthe platform is displaced vertically to form a subsequent layer,light-polymerizable material is then added to the most recently formedlayer, and repetition of the foregoing steps leads to the layeredconstruction of the orthodontic bracket in the desiredprescription/mold, which arises from the succession of layer geometriesdetermined from the CAD software. The trough can be shifted horizontallyto a supply position, and the supply device brings light-polymerizablematerial at least to an illumination field of the trough bottom, beforethe at least one trough is shifted to an illumination position in whichthe illumination field is located below the platform and above theillumination unit, and illumination is carried out, creating a “greenbracket”.

The light-polymerizable material or photo-reactive suspension (slurry)can be prepared based on commercially available di- and mono-functionalmethacrylates. An example material might be a slurry blend of about 0.01to about 0.025 wt % of a highly reactive photoinitiator, about 0.05 toabout 6 wt % a dispersant, an absorber, and about 2 to about 20 wt % ofa non-reactive diluent. A solid loading of high strength Oxide ceramicssuch as Aluminum Oxide (Al₂O₃) and Zirconium Oxide (ZrO₂) powder can beused, but this process may extend to other ceramic materials.

An exemplary block diagram of a computer system 700, in which theprocesses shown above may be implemented, is shown in FIG. 7. Computersystem 700 is typically a programmed general-purpose computer system,such as a personal computer, workstation, server system, andminicomputer or mainframe computer. Computer system 700 includes one ormore processors (CPUs) 702A-702N, input/output circuitry 704, networkadapter 706, and memory 708. CPUs 702A-702N execute program instructionsin order to carry out the functions of embodiments of the presentinvention. Typically, CPUs 702A-702N are one or more microprocessors,such as an INTEL PENTIUM® processor. FIG. 7 illustrates an embodiment inwhich computer system 700 is implemented as a single multi-processorcomputer system, in which multiple processors 702A-702N share systemresources, such as memory 708, input/output circuitry 704, and networkadapter 706. However, the present invention also contemplatesembodiments in which computer system 700 is implemented as a pluralityof networked computer systems, which may be single-processor computersystems, multi-processor computer systems, or a mix thereof.

Input/output circuitry 704 provides the capability to input data to, oroutput data from, computer system 700. For example, input/outputcircuitry may include input devices, such as keyboards, mice, touchpads,trackballs, scanners, etc., output devices, such as video adapters,monitors, printers, etc., and input/output devices, such as, modems,etc. Network adapter 706 interfaces device 700 with a network 710.Network 710 may be any public or proprietary LAN or WAN, including, butnot limited to the Internet.

Memory 708 stores program instructions that are executed by, and datathat are used and processed by, CPU 702 to perform the functions ofcomputer system 700. Memory 708 may include, for example, electronicmemory devices, such as random-access memory (RAM), read-only memory(ROM), programmable read-only memory (PROM), electrically erasableprogrammable read-only memory (EEPROM), flash memory, etc., andelectro-mechanical memory, such as magnetic disk drives, tape drives,optical disk drives, etc., which may use an integrated drive electronics(IDE) interface, or a variation or enhancement thereof, such as enhancedIDE (EIDE) or ultra-direct memory access (UDMA), or a small computersystem interface (SCSI) based interface, or a variation or enhancementthereof, such as fast-SCSI, wide-SCSI, fast and wide-SCSI, etc., orSerial Advanced Technology Attachment (SATA), or a variation orenhancement thereof, or a fiber channel-arbitrated loop (FC-AL)interface.

The contents of memory 708 varies depending upon the function thatcomputer system 700 is programmed to perform. In the example shown inFIG. 7, memory contents that may be included in a system in which acontent analysis platform is implemented are shown. However, one ofskill in the art would recognize that these functions, along with thememory contents related to those functions, may be included on onesystem, or may be distributed among a plurality of systems, based onwell-known engineering considerations. Embodiments of the presentinvention contemplate any and all such arrangements.

In the example shown in FIG. 7, memory 708 may include dentition datameasurement routines 712, 3D CAD teeth model construction routines 714,3D CAD teeth model editing routines 716, bracket design routines 718,manufacturing control data generation routines 720, and operating system722. Dentition data measurement routines 712 may obtain and processdentition data, such as may be generated by CT layer scanning or anon-contact 3D scanner directly on the patient's teeth, or uses 3Dreadings on the teeth model previously cast. 3D CAD teeth modelconstruction routines 714 may construct a 3D CAD model of the measuredteeth based on the dentition data. 3D CAD teeth model editing routines716 may be used to re-arrange the teeth in the model to the desiredtreatment outcomes and may additionally be used to accept additionalinformation, such as the desired torque, offset, angulation of selectbrackets and occlusal/incisal coverage for placement guide. Bracketdesign routines 718 may be used to design and generate a 3D CAD modelbased on the input 3D CAD model of the measured teeth, the model of thedesired treatment outcomes, and the input additional information.Manufacturing control data generation routines 720 may be used togenerate manufacturing control data for use by the production equipment.Operating system 722 provides overall system functionality.

It is to be noted that additional functionality may be implemented inend user devices, such as end user devices 104 shown in FIG. 1. End usersystems may be computer systems having a structure similar to that shownin FIG. 7. Such end user systems may include geometric analysis routinesto perform geometric analysis of a location of an advertisement orcontent, such as may be performed by step 302 of FIG. 3. Likewise, suchend user systems may include resource-based analysis routines todetermine whether a computer is optimizing an advertisement or contentfor display on the screen, such as may be performed by step 302 of FIG.3.

As shown in FIG. 7, an embodiment of the present invention contemplatesimplementation on a system or systems that provide multi-processor,multi-tasking, multi-process, and/or multi-thread computing, as well asimplementation on systems that provide only single processor, singlethread computing. Multi-processor computing involves performingcomputing using more than one processor. Multi-tasking computinginvolves performing computing using more than one operating system task.A task is an operating system concept that refers to the combination ofa program being executed and bookkeeping information used by theoperating system. Whenever a program is executed, the operating systemcreates a new task for it. The task is like an envelope for the programin that it identifies the program with a task number and attaches otherbookkeeping information to it. Many operating systems, including Linux,UNIX®, OS/2®, and Windows®, are capable of running many tasks at thesame time and are called multitasking operating systems. Multi-taskingis the ability of an operating system to execute more than oneexecutable at the same time. Each executable is running in its ownaddress space, meaning that the executables have no way to share any oftheir memory. This has advantages, because it is impossible for anyprogram to damage the execution of any of the other programs running onthe system. However, the programs have no way to exchange anyinformation except through the operating system (or by reading filesstored on the file system). Multi-process computing is similar tomulti-tasking computing, as the terms task and process are often usedinterchangeably, although some operating systems make a distinctionbetween the two.

An example of an orthodontic bracket 800 is shown in FIG. 8. In thisexample, the base 802 of the bracket is shown to the left and the face804 of the bracket is shown to the right. Base 802 is the portion thatcomes into contact with the tooth, and face 804 includes slot 806, whichin embodiments may be a mesial-distal slot adapted to receive anarchwire for applying force to a tooth.

An example of an orthodontic bracket 900 is shown in FIG. 9. In thisexample, the base 902, face 904, and slot 906 are shown. Also shown arethe desired slot wall position 908 and a compensation angle 910 for thewalls 912 of slot 906, which may be utilized to counteract shrinkage dueto over-polymerization and achieve parallel slot walls 912 of a desireddimension. In embodiments, slot 906 may be a mesial-distal slot adaptedto receive an archwire for applying force to a tooth. Slot 906 may beinitially manufactured with a “dovetail” cross-section includingcompensation angle 910, so that the finished bracket may achieveparallel slot walls of a desired dimension, as shown by desired slotwall position 908.

An example of an orthodontic bracket 1000 is shown in FIG. 10. In thisexample, a fracture wall 1002 may be manufactured around the perimeterof the base 1004 of bracket 1000. In embodiments, fracture wall 1002 mayhave a consistent thickness, which may be in a range of 15-140 μm,inclusive. In embodiments, fracture wall 1002 may have a varyingthickness, which may be in a range of 15-140 μm, inclusive. Inembodiments, bonding cement may be inserted into the cavity formed byfracture wall 1002. In embodiments, the wall thickness may be consistentaround all edges of bracket 1000, enabling a normal force 1006 (thecomponent of the contact force that is perpendicular to the surface offracture wall 1002) to be applied in any direction, such asmesial-distal, occlusal-gingival, or to any opposite corners. Thecontinuity of fracture wall 1002 around the entire bracket may providepredictable fracture of the wall via pliers, enabling debonding of thebracket though a combination of tensile and peeling forces, which istypically less than the shear bond strength of a bonded bracket. Forexample, pliers may be used that may, moving around the ligated wire,induce a mesial-distal force 1006 on the labial portion of the bracket.In embodiments, such force may be in range of 10-180 Newtons, inclusive.Also shown in this example are slot 1008 (archwire/mesial-distal slot)and auxiliary slot 1010.

An example of an orthodontic bracket 1100 bonded to a tooth 1102 isshown in FIG. 11. This example depicts a bracket 1100 having a basesurface 1102 that is contoured 1104 to the shape of tooth 1102, such asalong a bracket/tooth interface 1106. The contouring 1104 may beconfigured to match the desired position of bracket 1100 on the tooth.Any changes in positioning of the bracket may require changes incontouring 1104. Base 1102 may be contoured to the tooth while thebracket face 1108 and slot 1110 may be aligned to a pre-prescribedlocation that includes variables typically accounted for in anorthodontic bracket prescription, including, for example 1) in/out andoffset, 2) tip and 3) torque. For example, an in/out position and offsetmay involve bracket thickness and offset relative to a tooth alongbracket/tooth interface 1106. A tip parameter may involve an angulationof slot 1110 along a mesio-distal direction. A torque parameter mayinvolve an inclination of slot 1110 and/or base 1102 relative to a toothsurface so that torque may be applied by an archwire.

An example of an orthodontic bracket 1200 is shown in FIG. 12. In thisexample, a fracture groove 1202 may be manufactured within the middlevertical third of ceramic bracket 1200, as viewed from the base 1204 ofbracket 1200. Contoured portion 1206 of base 1204 is also shown.

An example of an orthodontic bracket 1300 is shown in FIG. 13, as viewedfrom the base of bracket 1300. In this example, the mesial third 1302,the middle third 1304, and the distal third 1306, of bracket 1300, areindicated. A fracture groove 1308 may be manufactured within the middlevertical third 1304 on the tooth-contacting side of the ceramic bracket1300.

An example of an orthodontic bracket 1400 is shown in FIG. 14, in across-sectional view. In the example shown in FIG. 14, a fracture groove1402, horizontal (mesial-distal) slot 1404, and auxiliary slot 1406 areshown. Fracture groove 1402 may include a weakened area including atooth curved depression (groove) in the bracket base 1408 runningvertically (in the occlusal-gingival direction) within the middle thirdof bracket 1400. Fracture groove 1402 may match the contour of the toothfor that portion of the bracket positioning. Fracture groove 1402 mayalign with the vertical midline and/or deepest portion of auxiliary slot1406. The bracket area between these features may form the weakened areaof bracket 1400.

Finite-element analysis has revealed that mesial-distal forces on theside of the tie-wings results in a concentration of forces in the middlethird of the bracket base. In embodiments, fracture groove 1402 may bedefined as an area of removed material from where such forces would havebeen most concentrated. The addition of fracture groove 1402 lowers theforces required to predictably create a bracket fracture down the middlevertical third of the bracket, which aids in debonding the ceramicbracket from the tooth. The weakened area and the fracture force can beoptimized by adjusting the dimensions of the groove and/or the auxiliaryslot.

In embodiments, fracture groove 1402 may be constant in depth from thetooth surface, as shown in FIG. 14. In embodiments, constant depthfracture groove 1402 may be a nominal or predetermined depth for some orall brackets for a patient. For example, groove depths 1410, 1412, and1414 may all be the same predetermined depth “X”. Such a nominal orpredetermined depth may be in a range of, for example, 0.10 mm to 1.2mm, inclusive. In embodiments, constant depth fracture groove 1402 maybe a depth that is different for some or for each bracket. For example,a distance from the tooth surface to the deepest part of fracture groove1402 may differ for different brackets.

An example of an orthodontic bracket 1500 is shown in FIG. 15, in across-sectional view. In embodiments, fracture groove 1502 may bevariable in depth from the tooth surface, as shown in FIG. 15. Inembodiments in which fracture groove 1502 is variable, the variance mayhave a range of 1-50%, inclusive, of the distance from the tooth surfaceto the deepest part of fracture groove. For example, groove depth 1510may be depth “X”, groove depth 1512 may be depth “Y”, and groove depth1514 may be depth “Z”. In embodiments, variable depth fracture groove1502 may have a nominal or predetermined maximum depth for some or allbrackets for a patient. Such as nominal or predetermined maximum depthmay be in a range of, for example, 0.10 mm to 1.2 mm, inclusive. Inembodiments, constant depth fracture groove 1502 may have a maximumdepth that is different for some or for each bracket. For example, adistance from the tooth surface to the deepest part of fracture groove1502 may differ for different brackets.

An example of an orthodontic bracket 1600 is shown in FIG. 16. In thisexample, plurality of retentive structures 1602 are shown included inbase 1604 of bracket 1600. An example of a retentive structure 1700 isshown in FIG. 17, in cross-section. In embodiments, retentive structure1700 may be of any shape which is a three-dimensional figure with apositive draft angle greater than 0°. Draft angle 1702 may be an anglebetween a perpendicular to neutral plane 1704, which may be orientedtoward a tooth structure or surface, and a sidewall 1706 of retentivestructure 1700. In embodiments, in cross-section, retentive structure1700 may be generally trapezoidal, with a neutral plane 1704, which maybe a plane oriented toward a tooth structure or surface, being widerthan a base plane 1708, which may be a plane on a side of the retentivestructure 1700 oriented toward a bracket body. Neutral plane 1704 may beflat or may be contoured to the shape of the tooth surface to which itis meant to be bonded. In embodiments in which a neutral plane 1704 ofeach retentive structure is flat, neutral planes 1704 of all retentivestructures may be parallel to base plane 1708, or a neutral plane 1704of some or all retentive structures may not be parallel to base plane1708, such that the overall pattern of retentive structures may begenerally contoured to the tooth surface. Further the parallel ornon-parallel alignment of neutral plane 1704 and base plane 1708 mayaffect the draft angle 1702 for each retentive structure 1700. Whilesuitable retention may be achieved with bonding cement, a range ofdesigned draft angles 1702 may be utilized to compensate for thelimitations of particular three-dimensional printing processes. Forexample, to achieve a desired final draft angle, the design of thedigital file's draft angle may need to be increased to compensate forover-polymerization, polymerization-shrinkage and any othercompensations. If a zero or positive draft angle is achieved from theactual printed part (regardless of the digital file design), suitableretention should be achievable.

In the example shown in FIG. 16, retentive structures 1602 are shown assemi-lunar cones. However, in embodiments, retentive structures 1602 maybe semi-lunar cones, full-circle cones, squares, rectangles, retentivelattices or meshes, or any other shape having a positive draft angle atany point meant to enhance bond strength. Such shapes having a positivedraft angle may be more efficiently manufactured by three-dimensionalprinting rather than by injection molding or casting methods.

An example of an orthodontic bracket 1800 is shown in FIG. 18. In theexample shown in FIG. 18, the retentive structures 1802 are showncontoured to the tooth surface looking from the inside of a tooth (asshown in a three-dimensional vector (e.g. .stl or additive manufacturingfile format (AMF)) representation). Each structure may be contoured tofit its corresponding area of tooth surface within the prescribedbracket position.

An example of an orthodontic bracket 1900 is shown in FIG. 19. In thisexample, bracket base cavity 1902 is also contoured to ensure eachretentive structure maintains its dimensions and all structures have asimilar depth. Further, a depth 1904 of contoured cavity 1902 may bedefined.

An example of an orthodontic bracket 2000 is shown in FIG. 20. In thisexample, the gingival corners 2002 of bracket 2000 may be rounded toaccount for the keratinized/attached gingiva, which would normallyinterfere with the bracket bonding surface. The roundness and radius ofthese corners may be changed from patient to patient, and within a case,from tooth to tooth, and is determined based on the doctor's desire toplace the bracket (and slot) further gingival on the tooth than wouldtypically be allowed by a stock bracket with a stock base. Inembodiments, a radius of curvature of rounded gingival corners 2002 maybe in a range of 0.05 to 2.0 mm, inclusive.

An example of a process 2100 of bracket design is shown in FIG. 21. Inthe example shown in FIG. 21, process 2100 includes the use of two majorsoftware design tools, AUTODESK MESHMIXER® 2102 and SOLIDWORKS® 2014.Although these two software packages are utilized for this example, anysoftware tools capable of performing mesh modeling, such as triangularmesh modeling, and solid modeling, may be utilized. Process 2100 beginswith 2106, in which an Extruded Base Bracket (EBB) model 2108 may beuploaded to an occluded tooth position (OTP) file 2110 to produce aBracket Placement (BP) file 2111. EBB model 2108 may define a default orinitial base design that will be modified by process 2100. OTP file 2110may include models of the positions, shapes, and contours of the teethto which brackets are to be attached. At 2112, initial EBB model 2108may be positioned on a tooth included in BP file 2111. Once the bracketposition is determined, at 2114, initial EBB model 2108 may be modifiedto incorporate the tooth surface at the determined bracket position toproduce Contoured Base Bracket (CBB) model 2116. For example, a Booleandifference operation between EBB model 2108 and the tooth surface datain the OTP file 2110 may be performed to produce Contoured Bracket Basemodel 2116.

At 2118, the base surface of CBB 2116 may be separated to form a newpart model, CBB-Tool 2120. At 2122, CBB-Tool model 2120 may be modifiedby extruding CBB-Tool model 2120 by a desired cavity depth, such ascavity depth 1904, shown in FIG. 19. At 2124, CBB and modified CBB-Tool2126 may be exported from a mesh modeling tool, such as MESHMIXER® 2102to a solid modeling tool, such as SOLIDWORKS® 2104.

At 2128, CBB and modified CBB-Tool 2126 may be uploaded and saved, forexample, as .part files. At 2136, a solid model of the tool assembly(TA) 2138 may be created from modified CBB-Tool and from one or morefiles defining the retentive structures 1700, such as cones, etc., shownin FIG. 17. At 2140, a cavity of each retentive structure may be createdwithin modified CBB-Tool to make a retentive CBB-Tool (RCCB-Tool) 2141.At 2130, a solid model of the bracket assembly (BA) 2132 may be createdfrom CBB and RCBB-Tool 2141. At 2134, RCBB-Tool may be mated to CBB. At2142, a cavity of RCBB-Tool may be created within CBB to form a finishedsolid model (SM) of a bracket including retentive structures 2144.

It is important to note that while aspects of the present invention maybe implemented in the context of a fully functioning data processingsystem, those of ordinary skill in the art will appreciate that theprocesses of an embodiment of the present invention are capable of beingdistributed in the form of a computer program product including acomputer readable medium of instructions. Examples of non-transitorycomputer readable media include storage media, examples of whichinclude, but are not limited to, floppy disks, hard disk drives,CD-ROMs, DVD-ROMs, RAM, and, flash memory.

Although specific embodiments of the present invention have beendescribed, it will be understood by those of skill in the art that thereare other embodiments that are equivalent to the described embodiments.Accordingly, it is to be understood that the invention is not to belimited by the specific illustrated embodiments, but only by the scopeof the appended claims.

What is claimed is:
 1. A method for use in manufacturing customizedceramic labial/lingual orthodontic brackets by additive manufacturing,the method comprising: accessing dentition data of a profile of apatient's teeth; based on the dentition data, generating athree-dimensional (3D) model of the patient's teeth; generating a 3Dmodel of a labial/lingual bracket structure based on the 3D model of thepatient's teeth, the labial/lingual bracket structure comprising afracture groove; transmitting data indicating the 3D model of thelabial/lingual bracket structure to an additive manufacturing machinefor production of a bracket using the 3D model of the labial/lingualbracket structure.
 2. The method of claim 1, wherein the labial/lingualbracket structure comprises: a bracket body comprising a slot; whereinthe fracture groove is disposed in relation to the slot.
 3. The methodof claim 2, wherein: the bracket body comprises a mesial tie wing pairand a distal tie wing pair; and the body comprises an arch wire slotcomprising slot walls formed at least partially by the mesial tie wingpair and the distal tie wing pair.
 4. The method of claim 3, wherein theslot is an auxiliary slot between the mesial tie wing pair and thedistal tie wing pair.
 5. The method of claim 4, wherein the fracturegroove is at least partially aligned with the auxiliary slot.
 6. Themethod of claim 1, wherein the fracture groove is located in amiddle-vertical third of the 3D model of the labial/lingual bracketstructure.
 7. The method of claim 1, wherein the fracture groovecomprises a weakened area of the labial/lingual bracket structure. 8.The method of claim 4, wherein the weakened area of the labial/lingualbracket structure comprises a depression within the labial/lingualbracket structure in an occlusal-gingival direction.
 9. The method ofclaim 1, wherein fracture groove has a negative draft angle.
 10. Themethod of claim 1, wherein the additive manufacturing machine isconfigurable to produce the bracket from an inorganic material.
 11. Themethod of claim 9, wherein the inorganic material comprises at least oneof a ceramic or a metal.
 12. The method of claim 11, wherein the ceramicis a polymer-derived ceramic, and the metal is a polymer-derived metal.13. The method of claim 1, wherein a contour of a surface of thelabial/lingual bracket structure has a contour based on a shape of aportion of a tooth of the 3D model of the patient's teeth to which thebracket is to be bonded.
 14. The method of claim 1, wherein thelabial/lingual bracket structure comprises a bracket pad configured tooppose a tooth surface, wherein the bracket pad comprises the fracturegroove.
 15. The method of claim 1, wherein fracture groove comprises asurface that matches a contour of a portion of a tooth of the 3D modelof the patient's teeth to which the bracket is to be bonded.
 16. Themethod of claim 1, the fracture groove has a depth from a surface of atooth, of the 3D model of the patient's teeth to which the bracket is tobe bonded, approximately constant throughout the fracture groove. 17.The method of claim 16, wherein the constant depth is in a range ofapproximately 0.10 millimeters to 1.2 millimeters.
 18. A customizedceramic labial/lingual orthodontic bracket comprising: a fracturegroove; wherein the customized ceramic labial/lingual orthodonticbracket is produced by additive manufacturing using a 3D model of alabial/lingual bracket structure and a 3D model of a patient's teeth.19. The customized ceramic labial/lingual orthodontic bracket of claim18, further comprising: a slot, wherein the fracture groove is disposedin relation to the slot.
 20. The customized ceramic labial/lingualorthodontic bracket of claim 19, further comprising: a mesial tie wingpair and a distal tie wing pair; and an arch wire slot comprising slotwalls formed at least partially by the mesial tie wing pair and thedistal tie wing pair.
 21. At least one non-transitory computer-readablestorage medium encoded with a plurality of computer-executableinstructions that, when executed by one or more processors, are operableto cause the one or more processors to perform a method formanufacturing a customized ceramic labial/lingual orthodontic bracket,the method comprising: importing a 3D model of a labial/lingual bracketstructure generated based on a 3D model of a patient's teeth, whereinthe 3D model includes data representing a fracture groove; and using theadditive manufacturing machine to form, based on the 3D model of thelabial/lingual bracket structure, the customized ceramic labial/lingualorthodontic bracket with the fracture groove.